From 8336dd4c16d4885989a6d8f0c83a4b401f5cb63b Mon Sep 17 00:00:00 2001 From: Boris Kolpackov Date: Thu, 2 Apr 2009 12:22:38 +0200 Subject: Add support for attributes with default and fixed values. tests/cxx/hybrid/default: new test tests/cxx/hybrid/binary: update to test default and fixed values --- documentation/cxx/hybrid/guide/index.xhtml | 138 ++++++++++++++++++++++++++++- documentation/xsde.1 | 4 + documentation/xsde.xhtml | 4 + 3 files changed, 145 insertions(+), 1 deletion(-) (limited to 'documentation') diff --git a/documentation/cxx/hybrid/guide/index.xhtml b/documentation/cxx/hybrid/guide/index.xhtml index 5871593..d497a14 100644 --- a/documentation/cxx/hybrid/guide/index.xhtml +++ b/documentation/cxx/hybrid/guide/index.xhtml @@ -2031,7 +2031,143 @@ if (p.middle_name_present ()) } -

Finally, the sequence cardinality class covers all elements +

There are two cases in the optional cardinality class that + are handled differently. These are optional attributes with default + and fixed values. When an optional attribute declaration in XML Schema + specifies a default or fixed value and such an attribute is not present + in the XML document, the attribute is assumed to have the default or + fixed value, respectively. Furthermore, if an attribute with the + fixed value is set in the XML document, then the attribute value + should be the same as its fixed value.

+ +

For an optional attribute with a default value, the functions for + querying and modifying the attribute's presence status are replaced + with functions that allow you to determine whether the attribute has + the default value. The accessor functions can be called at any time + since an optional attribute with a default value always has some + value. Also an extra static function is provided to allow you to + obtain the default value. Consider the following modification to + the person type which adds the verified + attribute with the default value:

+ + 
+<xs:complexType name="person">
+  <xs:sequence>
+    <xs:element name="first-name" type="xs:string"/>
+    ...
+  </xs:sequence>
+  <xs:attribute name="id" type="xs:unsignedInt" use="required"/>
+  <xs:attribute name="verified" type="xs:boolean" default="false"/>
+</xs:complexType>
+
+ +

The code fragment below shows the accessor and modifier functions + that are generated for this new attribute in the person + class:

+ + 
+class person
+{
+  // verified
+  //
+  bool
+  verified_default () const;
+
+  void
+  verified_default (bool);
+
+  bool
+  verified () const;
+
+  bool&
+  verified ();
+
+  void
+  verified (bool);
+
+  static bool
+  verified_default_value ();
+};
+
+ +

When we create an object of the person class, the + verified member is automatically initialized to the + default value. The following example shows how we can manipulate + the verified attribute value:

+ + 
+person p; // verified is set to the default value (false).
+
+if (p.verified_default ())
+  p.verified (true);
+else
+  p.verified_default (true); // Revert to the default value.
+
+bool v = p.verified (); // Ok, can always be called.
+bool vd = person::verified_default_value ();
+
+ +

Note that modifying an attribute of a variable-length type via + the reference when the attribute is set to the default value is + illegal since this will modify the default value shared by all + instances. For example:

+ + 
+type& x = ...
+
+if (x.foo_default ())
+{
+  foo& f = x.foo (); // foo is variable-length, for example NMTOKENS
+  f.push_back ("aaa"); // Illegal.
+}
+
+if (x.foo_default ())
+{
+  foo* f = new foo;
+  f->push_back ("aaa");
+  x.foo (f); // Ok.
+}
+
+ +

Because an attribute with a fixed value can only be set to that + value, only the read-only (constant) accessor and the static + function for obtaining the fixed value are provided for such + attributes. Similar to the default values, members with fixed + values of a newly created object are automatically initialized + to their respective fixed values. Consider the following + modification to the verified attribute from the + schema above:

+ + 
+<xs:complexType name="person">
+  ...
+  <xs:attribute name="verified" type="xs:boolean" fixed="true"/>
+</xs:complexType>
+
+ +

The code fragment below shows the accessor functions that are + generated for this attribute in the person + class:

+ + 
+class person
+{
+  // verified
+  //
+  bool
+  verified () const;
+
+  static bool
+  verified_fixed_value ();
+};
+
+ +

During serialization, attributes that are set to default and fixed + values are explicitly specified in the resulting XML document. + You can use the --omit-default-attributes XSD/e + compiler option to omit such attributes from the serialized XML.

+ +

The sequence cardinality class covers all elements that can occur more than once. In our example, the person element in the people type belongs to this cardinality class. The following code fragment shows diff --git a/documentation/xsde.1 b/documentation/xsde.1 index 62cc55d..874a4de 100644 --- a/documentation/xsde.1 +++ b/documentation/xsde.1 @@ -944,6 +944,10 @@ Suppress the generation of validation code in parser. .IP "\fB\--suppress-serializer-val\fR" Suppress the generation of validation code in serializer. +.IP "\fB\--omit-default-attributes\fR" +Omit attributes with default and fixed values from serialized XML +documents. + .IP "\fB\--generate-detach\fR" Generate detach functions for elements and attributes of variable-length types. These functions, for example, allow you to move sub-trees in the diff --git a/documentation/xsde.xhtml b/documentation/xsde.xhtml index c8f602a..697c751 100644 --- a/documentation/xsde.xhtml +++ b/documentation/xsde.xhtml @@ -816,6 +816,10 @@

--suppress-serializer-val
Suppress the generation of validation code in serializer.
+
--omit-default-attributes
+
Omit attributes with default and fixed values from serialized + XML documents.
+
--generate-detach
Generate detach functions for elements and attributes of variable-length types. These functions, for example, allow -- cgit v1.1